In case of wideband telecommunications systems, in order to maximize the efficiency of limited wireless (or radio) resources, a number of more effective transmitting and receiving methods in time, space, and frequency domains and the respective application methods have been proposed. Particularly, the multi carrier OFDM method has the advantages of reducing the complexity of a receiving end in a frequency selective fading environment that occurs in a wideband channel and, also, of maximizing spectral efficiency through selective scheduling in a frequency domain by applying different channel characteristics (or attributes) of a subcarrier. Furthermore, by allocating (or assigning) different subcarriers to multiple users, the OFDM method is extendable to an orthogonal frequency division multiple access (OFDMA) method, thereby being capable of enhancing the efficiency of the wireless resource in the frequency domain.
As the WirelessMAN-OFDMA standard adopting the typical OFDMA, IEEE 802.16-2004 and the amended standard IEEE 802.16e−2005 (hereinafter referred to as IEEE 802.16e) have been completed.
FIG. 1 shows a logical frame structure of the IEEE 802.16e system. As shown in FIG. 1, the logical frame structure of the IEEE 802.16e system consists of a preamble (101), an FCH (frame control header) (102), control signal blocks of DL/UL-MAP (103, 104), and data bursts. Also, the data transmission of each user is defined by different subcarrier allocation methods (e.g., PUSC, (O)-FUSC, TUSC, AMC, etc.) depending upon the method of configuring the subcarrier. Herein, various permutation zones may be configured in one frame.
In the frame of the IEEE 802.16e system, as shown in FIG. 1, the reception of an initial preamble (101), an FCH (102), and control information on the DL/UL-MAP (103, 104) is required. And, the role of each field is as follows:                Preamble (101): performing synchronization, channel estimation, cell ID acquisition, etc.        FCH (102): providing channel allocation information and channel code information associated with the DL-MAP (103)        DL/UL-MAP (103, 104): providing channel allocation information of a data burst in an downlink (DL)/uplink (UL)        
Among the above-described control fields, with the exception of the preamble (101), the logical frame structure may be diversely configured (or established) in accordance with a subchannel allocation method (PUSC, (O)-FUSC, TUSC, AMC, etc.) selected by taking into consideration factors such as frequency diversity gain, scheduling gain, convenience in adopting a pilot overhead or multi/adaptive antenna.
Meanwhile, discussions of an enhanced version (or system) of the above-described IEEE 802.16e system is in progress, and such system will be regulated as the IEEE 802.16m standard. Accordingly, reference may be made to “IEEE 802.16m-07/002r4—TGM System Requirements Document” (hereinafter referred to as “SRD”) for the requirements that the IEEE 802.16m system should satisfy.
Referring to the above-described SRD of the IEEE 802.16m system, it is mentioned that co-existence with the TD-SCMA, 3GPP LTE TDD should be supported in the IEEE 802.16m TDD mode. However, in case of the IEEE 802.16m system, an accurate frame structure has not yet been decided, and, accordingly, discussions on the uplink/downlink ratio and time domain structure of a frame within the IEEE 802.16m system for the co-existence with the heterogeneous TDD system is required to be made.